Buggy code:
public class XPathUtil { private static final Logger LOGGER = LoggerFactory . getLogger ( XPathUtil . class ) ; public static Expr parseXPath ( final String xpath ) { } private static String asString ( final PrintStream ps , ByteArrayOutputStream os ) throws UnsupportedEncodingException { } private static void close ( final PrintStream ps , final ByteArrayOutputStream os ) { } public static boolean isSubset ( final String subset , final String superset ) { } public static boolean isSubset ( final Expr subset , final Expr superset ) { if ( ! ( XPathUtil . isAbsolutePathExpr ( subset ) ) ) { throw new IllegalArgumentException ( "Subset<seq2seq4repair_space>expression<seq2seq4repair_space>must<seq2seq4repair_space>be<seq2seq4repair_space>an<seq2seq4repair_space>absolute<seq2seq4repair_space>path<seq2seq4repair_space>expression" ) ; } if ( ! ( XPathUtil . isAbsolutePathExpr ( superset ) ) ) { throw new IllegalArgumentException ( "Superset<seq2seq4repair_space>expression<seq2seq4repair_space>must<seq2seq4repair_space>be<seq2seq4repair_space>an<seq2seq4repair_space>absolute<seq2seq4repair_space>path<seq2seq4repair_space>expression" ) ; } final List < ? extends StepExpr > subsetSteps = XPathUtil . getSteps ( subset ) ; final List < ? extends StepExpr > supersetSteps = XPathUtil . getSteps ( superset ) ; int subsetIdx = 0 ; int supersetIdx = 0 ; while ( ( subsetIdx < ( subsetSteps . size ( ) ) ) && ( supersetIdx < ( supersetSteps . size ( ) ) ) ) { final StepExpr subsetStep = subsetSteps . get ( subsetIdx ) ; final StepExpr supersetStep = supersetSteps . get ( supersetIdx ) ; if ( subsetStep . equals ( SLASH_ABBREV ) ) { if ( supersetStep . equals ( SLASH_ABBREV ) ) { subsetIdx ++ ; supersetIdx ++ ; continue ; } else if ( supersetStep . equals ( SLASH_SLASH_ABBREV ) ) { final StepExpr supersetNextStep = supersetSteps . get ( ( ++ supersetIdx ) ) ; <START_BUG> while ( subsetIdx < ( subsetSteps . size ( ) ) ) { <END_BUG> if ( XPathUtil . isSubsetStep ( ( ( AxisStep ) ( subsetSteps . get ( ( ++ subsetIdx ) ) ) ) , ( ( AxisStep ) ( supersetNextStep ) ) ) ) { subsetIdx ++ ; break ; } } supersetIdx ++ ; } } else if ( subsetStep . equals ( SLASH_SLASH_ABBREV ) ) { if ( supersetStep . equals ( SLASH_SLASH_ABBREV ) ) { final StepExpr supersetNextStep = supersetSteps . get ( ( ++ supersetIdx ) ) ; while ( subsetIdx < ( ( subsetSteps . size ( ) ) - 1 ) ) { if ( XPathUtil . isSubsetStep ( ( ( AxisStep ) ( subsetSteps . get ( ( ++ subsetIdx ) ) ) ) , ( ( AxisStep ) ( supersetNextStep ) ) ) ) { subsetIdx ++ ; break ; } } supersetIdx ++ ; } else if ( supersetStep . equals ( SLASH_ABBREV ) ) { break ; } } else if ( ( subsetStep instanceof AxisStep ) && ( supersetStep instanceof AxisStep ) ) { if ( XPathUtil . isSubsetStep ( ( ( AxisStep ) ( subsetStep ) ) , ( ( AxisStep ) ( supersetStep ) ) ) ) { subsetIdx ++ ; supersetIdx ++ ; continue ; } else { break ; } } } return subsetIdx > ( ( subsetSteps . size ( ) ) - 1 ) ; } public static boolean isSubsetStep ( final AxisStep subset , final AxisStep superset ) { } public static boolean isSubsetAxis ( final Axis subset , final Axis superset ) { } public static boolean isSubsetNodeTest ( final NodeTest subset , final Axis subsetAxis , final NodeTest superset ) { } public static boolean isSubsetNameTest ( @ Nullable final QNameW subset , @ Nullable final QNameW superset ) { } public static boolean isAbsolutePathExpr ( final String expr ) { } public static boolean isAbsolutePathExpr ( final Expr expr ) { } public static List < ? extends StepExpr > getSteps ( final Expr expr ) { } }

Fix:
while ( subsetIdx < ( ( subsetSteps . size ( ) ) - 1 ) ) {